In thermally assisted magnetic recording, information bits are recorded on a data storage medium at elevated temperatures, and the heated area in the storage medium determines the data bit dimension. In one approach, a beam of light is condensed to a small optical spot onto the storage medium to heat a portion of the medium and reduce the magnetic coercivity of the heated portion. Data is then written to the reduced coercivity region.
Heat assisted magnetic recording (HAMR) has been developed to address instabilities that result from a reduction in grain size in magnetic recording media. HAMR generally refers to the concept of locally heating a storage medium to reduce the coercivity of the storage medium so that an applied magnetic writing field can more easily direct the magnetization of the storage medium during the temporary magnetic softening of the storage medium caused by the heat source. Heat assisted magnetic recording allows for the use of small grain media, which is desirable for recording at increased areal densities, with a larger magnetic anisotropy at room temperature to assure sufficient thermal stability.
One example of a recording head for use in heat assisted magnetic recording generally includes a write pole and a return pole magnetically coupled to each other through a yoke or pedestal, and a waveguide for focusing light onto the storage medium. One of the most challenging design requirements for an integrated HAMR head is in positioning the magnetic poles with respect to the focused spot in the waveguide. Magnetic materials such as alloys of Fe, Co and Ni are poor optical materials, so they cannot be positioned in close proximity with the waveguide for an appreciable distance.